Relief valve



0a. 31, 1944. R, S EPPARD 2,361,881

RELIEF VALVE Filed Oct. 10, 1942 Invent or Ragrnond Sheppard,

His Atbofney.

Patented Oct. 31, 1944 I RELIEF VALVE p Raymond Sheppard, Niskayuna; N.Y., assignor to General Electric Company, a corporation of New YorkApplication October 10, 1942, Serial No. 461,555 1 Claim. (01.137-53)The present invention relates to relief valves for relieving fluid froma system under pressure whenever the pressure exceeds a certainpredetermined value. Difliculties have heretofore been experienced Withsuch valve due to chattering of the movable valve member and theconsiderab noise created thereby in power plants.

The object of my invention is to provide an improved. construction of.relief valves whereby the aforementioned drawbacks are substantiallyeliminated.

- This is accomplished in accordance with my to move axially on the bolt26, thus changing the dashpot piston 3| i secured to, in the presentininvention by the provision of a relief valve with a movable valvemember of the piston type and a to dampen pulsations thereof due topulsations of the pressure to be relieved. The dashpot is arranged tooffer different resistances to movement in opposite directions.

For a better understanding of what I believe to be novel and myinvention, attention is directed to the followingdescriptio-n and theclaims appended thereto in connection with the accompanying drawing.

In the drawing Fig. 1 illustrates a sectional view of a relief valveembodying my invention; and Fig. 2 shows diagrammatically a modificationof apart of Fig.1. j

The arrangement shown in Fig. 1 comprises a casing l forming an inletopening H and an outlet or discharge opening |2. The inlet opening isconnected to a system containing fluid under pressure, in the presentinstance indicated by a conduit l3 flanged to the casing I A cylindrical channel M with an annular recess or port l5 formed in the casingI0 connects the inlet H to the outlet l2. The flow of fluid through thecylindrical channel or cylinder is controlled by a piston type movablevalve member or plunger l6 slidably arranged within the cylinder I4 andnormally biased into closed position, as shown, by means including acompression spring I l. The lower end of said spring engages a. springplate l8 held on a shouldered extension or stem I9 of the piston [6 bymeans including a cotter pin 20.

'The upper-end of the spring |1 engages an upper spring plate 2| whichhas a lateral projection 22 engaging a guide 23 on the casing. In thepresent instance the guide 23 is formed on a cup-shaped casing cover 24secured to the casing by a pluralityv of bolts 25. The spring plate 2|is threaded onto a bolt 26 fastened to the cover 24 by means including anut 21. Loosening of the nut 21 and rotation of the bolt 26 cause thespring plate 2| stance integrally formed on, the. intermediate portionof the stem HI and slidably arranged within the dashpot cylinder 28.Upon movement of the piston 3| in the dashpot cylinder 28 fluid isdisplaced from the upper to the lower side of the piston 3| intwodistinct forms. One form of displacement of fluid is due to leakagealong the wall of .the cylinder-28 from the upper side to the lower sideof the piston 3|. This displacement or leakage of fluid along thecylinder wall takes place during both upward and downward travel of thepiston 3|. Another form of displacement of fluid is accomplished by theprovision of a bypass between the upper and lower ends of the cylinder28. This bypass in the present example is estab lished by channels 32and 33 connecting the upper and lower ends of the cylinder 28 to a checkvalve chamber 34 formed in the casing III. A ball-type valve member 35is disposed in the chamber 34 and biased towards a seat connecting thechamber to the channel 32 by means of a compression spring 36 held in aplug 31 screwed into an opening of the casing Ill. The valvedbypassedchannel including the channels 32, 33 and the check valve 35, 36permits displacement of fluid only from the upper side of the piston 3|to the lower side and does not permit displacement from the lower to theupper side of the piston 3|. Thus, upon upward movement of the piston 3|fluid may be displaced from the upper to the lower side thereof by bothforms, that is, by leakage of fluid along the piston 3| and bypassing offluid through th valved bypassed channel. Upon downward movement of thepiston 3|, however, fluid is dis placed from the lower side of thepiston to the upper side thereof I in the form of leakage only along thedashpot cylinder 28. Thus, the dashpot arrangement as shown forms asmall resistance against upward movement of the dashpot piston 3| andthe plunger or piston I6 connected thereto and a considerable resistanceagainst downward movement of the dashpot piston 3| permitting the piston3| and the plunger IE to move more rapidly in the upward than in thedownward direction. The dashpot cylinder 28 in the arrangement shown isfilled with the same fluid as that in the pressure system l3. If thelatter contains oil the cylinder 28 is filled with oil. Oil is conductedto the cylinder 28 by leakage along the walls of the cylinder I4. Fluidleaking along the lower end of the walls I4 is discharged through theannular port l5 to the outlet I2. In order to effect leakage along theupper wall portions of the cylinder I4 to the dashpot a channel 38 isformed in the piston l6 connecting the inlet I I to the upper wall ofthe cylinder I4 at a point above the annular port l5. During operation,fluid such as oil under pressure passes from the inlet through thechannel 38 and partly leaks upward along the wall of the cylinder l4into the dashpot cylinder 28 until the latter and the channels connectedthereto are substantially filled with such fluid. Y

A sudden considerable increase in pressure in the system I3 forces themovable valve member, that is, the piston l6, upward against the biasingforce of the spring I! and the restraining action of the dashpot 28, 3|.The restriction of the dashpot, as pointed out above, is small withregard to upward movement of the piston -3| because the fluid containedabove the piston may readily pass through the valved channels 32, 33 tothe lower side of the piston 3|. As the piston IS passes upward beyondthe lower edge of the port l5, fluid is discharged from the system I3through the inlet ll of the relief valve and the port I5 to its outletI'Z, whence the fluid may be returned to a reservoir through a conduit39 connected to the outlet I2. Upon discharge of fluid from the systemI3 through the relief valve the pressure in the system drops and as itreaches a predetermined value the movable valve member I6 is forceddownward into closing position by action of the spring II. This downwardmovement is considerably retarded by the dashpot 28, 3| which, aspointed out above, forms a considerable restriction against downwardmovement of the piston I6. A valve according to my invention may bemoved from closing to full opening position in a fraction of a secondwhile it may take six seconds to move the valve from opening to closingposition.

The dashpot due to its damping effect prevents opening of the valve inresponse to short pulsations of the fluid pressure in the system I3. If,however, a rapid succession of such pressure variations takes place inthe system 3 the movable valve member may be moved to opening positionto relieve some of the fluid under pressure. This is due to the factthat it takes the dashpot piston 3| a shorter period to move in upwarddirection than it takes the piston to return to its lower end position,engaging the bottom in the cylinder 28. Thus, in case of a succession ofpressure impulses a first pressure impulse may force the valve member 16upward a certain distance and the succeeding impulse, reaching its peakbefore the piston l6 has been returned to its original position, maymove the piston 3| further upward until a certain number of suchimpulses effect opening of the relief valve by moving the piston I6 upbeyond the lower edge of the port l5.

In the arrangement of Fig. l the restriction through the bypass channel32, 33 of the dashpot 28, 3| may be controlled by adjusting the plug 31on the casing to vary the biasing force of the spring 36 for theball-type valve member 35; This permits variation of the damping effectwith regard to upward movement of the dashpot piston 3|. In thediagrammatic view of Fig. 2 I have shown a dashpot arrangement whichmight be used in place of the dashpot arrangement in Fig. 1, permittingadjustment of the damping effect with regard to both upward and downwardmovement of the dashpot piston. The arrangement of Fig. 2 comprises adashpot cylinder 40 having a piston 4| movably disposed therein andconnected to a stem 42 corresponding to the stem I9 in Fig. 1. The upperand lower ends of the cylinder 40 are connected by two conduits orchannels, a wider channel 43 and a narrower channel 44. The widerchannel 43 corresponds to the channel 32, 33 of Fig. 1, and includes aball-type check valve 45 corresponding to the check valve 35, 36 ofFig. 1. This wider valved channel permits displacement of fluid onlyfrom the upper side of the piston 4| to the lower side thereof. Thenarrower channel or conduit 44 includes a check valve '46 of small sizearranged to permit displacement of fluid from the lower to the upperside only of the piston, 4|. The check valves 45 and 46 may be of thesame construction as the check valve 35, 36 in Fig. l, permittingadjustment to control displacement of fluid in either direction betweenthe upper and lower sides of the piston 4|.

Having described the method of operation of my invention, together withthe apparatus which I now consider to represent the best embodimentthereof, I desire to have it understood that the apparatus shown is onlyillustrative and that the invention may be carried out by other means.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

Relief valve comprising a casing having an inlet and an outlet andforming a cylindrical bore with a port for connecting the inlet to theoutlet, a plunger slidably disposed in the bore to control the port, acylindrical dashpot chamber in alignment with the bore, a piston securedto the plunger and slidably disposed in the chamber, adjustable springmeans normally biasing the plunger into an end position in which thepiston engages an end wall of the chamber and the pl 'un'ger covers theport, means for conducting fluid from the inlet to said cylindricalchamber including clearance space provided between the plunger and thebore and a channel in the plunger connecting the inlet side of theplunger to the side wall of the plunger at a point between the port andthe piston, and a check valve controlled bypass connecting the ends ofthe chamber to effect substantial dampening of the valve in onedirection only. v

RAYMOND SHEPPARD.

